Filter



Jan. 14, 1936! w. RAlscH 2,027,652-- FILTER Filed April 25, 1955 INVENTQR W 1151264117?, 120511567@ Patentedy Jan. 14, 1936 mman William Ralsch, Forest Hills, N. Y.,

assignor to Municipal Sanitary Service Corporation. New York, N. Y., a corporation of New York 'Applicationsipru 25, 1935, semi Nt. 1s,os':

iclaims. (ci. 21o- 201) The-present invention relates to lters 9i.' the rotary type and lmore particularly g to .means for stripping lter cake from the drum f, a 4rotary lter. f

'I'he main object of the invention relates to the provision of a novel and advantageous form oi' `filter cake stripping means. Other features of the invention relate to simplicity of construction, effectiveness of operation and-economy of manufacture and maintenance. f

According to one way of carrying out, the invention use may be made of a stripperin the form of a continuous belt or apron passing around rotary supports or rolls, one of which is located close to the surface of lthe fllter drum above the level of the liquid in the filter tank or pan so that members projecting from the belt so as to engage the filter cloth or other material at the surface of the drum may strip the filter cake therefrom, preferably with a spray of water di? rected upwardly between the filter drum and the stripper belt. The belt may be provided with stripping members in the form of ribs extending transversely of the belt and serving to wipe the lter cake, which is at the same time loosened and softened by the water spray, from the lter drum and convey it therefrom to any desired position. It will be evident that by this form of stripping device the cake can be removed from the drum near the top thereof and discharged at substantially any desired level. It may also be desirable to use a water Aspray in connection with the discharge of the cake.` It will be evident that the stripping means of the present in- Vention is particularly adapted for use in connection with apparatus in which the filter cake is repulped after stripping and returned to the sewage stream on its way to the filter. Apparatus of this general type is illustrated in the 4,0 Rausch a Wright Patent No. 1,937,481, Nov. 2a,

Other objects, features and advantages willv appear upon consideration of the following description and of the drawing, in which Fig. 1 is a view in vertical section of apparatus embodying one form of the invention;

Fig. 2 is a fragmentary perspective view on a larger scale showing the stripping action;

Fig. 3 is a fragmentary prospective view of one form of belt having stripping devices'thereon; and

Fig. 4 is a View similar to Fig. 3 but showing a modified form of belt.

Referring to. Fig. 1, the liquid to be filtered,

such as sewage, is supplied through a pipe I0 to a trough I and p asses therefrom `over a discharge or vveriioiv` walls I2 into. the Il of a rotary miser. Partially submerged in the liquid of the filter pan is a drum -|4 formed at its periphery with aplurality of compartments l, i

having at their outer sides lter means, which may include iilter cloth, and connected bypipes I6 to one or more rotary hubs, each of which cooperates with a fixed valve member Il .provided with partitions I9 and 2 0 setting'oif a cloudy ill- 10 trate chamber from which the cloudy ltrate is drawn oif through a suction or vacuum pipe 2|. The vacuum action in the pipe 2| may be effected in any suitable manner, as by utilizing the pipe 2| as barometric leg'. Each member Il 15 is also provided with a partition22 which Ataxogether with the partition 20 sets oi! a clear ill.- trate chamber from which the clear filtrate may be withdrawn througha section'of vacuum pipe 23 which may also serve as a barometric leg. It 20 will be seen that, asthe drum rotates in a clockwise direction, a cake will begin to form on the filter cloth or other mediums as soon as the vari-- ous compartments move into the liquid in the lter pan and'this cake will gradually increase 25 in thickness until it is raised out of the liquid in the pan. With the partition 22 in the position shown in Fig. 1, the cake willbe dried after bing moved out of the liquid and `will then be advanced under atmospheric pressure beyond the 30 top of the drum to a suitable place for stripping.

According tothe form illustrated in Figs. 1, 2 and 3, the stripping means comprising an endless belt 24 passing around rotatable supporting members 26 and 2B supported in any suitable 35 manner as by means of hangers 28 and 29 projecting downwardly from a beam or beams 30, the rotatable member 2i being relatively close to the lter drum |4. The belt 24 may be providedwith ribs or wipers 3| -to engage the filter medium at 40 the surface of the drum and convey the cake outwardly along the upper reach of the belt, the separation of the cake from the drum being fa' cilitated by a spray thrown upwardly along the drum from a spray device J2 comprising a pipe 45 extending along the drum and provided with outlets or nozzles at suitable intervals. The water for the jet device 82 maybe supplied through a pipe 32 which may also be used to furnish water to a jet device 34 so arranged as to-assist in dis- 50 charging the cake from the belt 24 as the latter passes downwardly around the rotatable member 26.. From the belt 24 the cake falls into the trough where it is mixed or repulped with the incoming sewage by means of a beater 35. 55

In the usual operation of the apparatus, a charge ofsuitable cake-forming material is placed in the nltei pan I3 to assurethe formation of a suitable cake to obtain proper clarincation of the nitrate. Then as the nlter drum revolves in clockwise direction (Fig. 1) each peripheral compartment I5 as it enters the liquid is subjected t0 the action of -the cloudy nitrate barometric leg 2l and the nlter cake begins to build up at the outer side of the compartment. At this time, however, the filter cake is so thin that various particles pass into the compartment and the nitrate at this time is cloudy. When, however, the compartment passes into .the zone of innuence of the clear nitrate barometric leg 23 the cake is of sufficient thickness to prevent the passage of solids of appreciable size therethrough and the resulting nitrate is clear. After leaving the liquid the compartment is still subjected to vacuum action and the cake at the surface thereof is dried. From the drying zone the compartment passes into an atmospheric pr this zone the cake is oved by the stripping means, the cake being loosened by the water spray or jets from the device 32 and then picked up by the ribs Il of the belt 2l by which the stripped cake is carried to a position over the repulping trough il into which it is discharged with the assistance of the water nowing in jets from the device 34. With this arrangement it will be evident that the cake forming material originally placed in the nlter pan I3 may be used and reused indefinitely. As illustrated in Fig. 2, after the discharge of the cake over the belt 24 has been started the cake will pass directly to the upper reach of the belt without being scraped from the belt by the ribs or wipers 3l, the space between the cake, the rotary member 25 and the drum being nlled with water and material removed directly from the drum by the ribs 3|.

In Fig. 4 there is illustrated a second form of belt 24a from outer face of which project fingers lla. The action of this form of belt in the stripping operations will be substantially the same as that of the beit shown in Figs. 1, 2 and 3 except that the nlter cloth at the periphery of the filter drum will not be wiped or brushed conure zone and while in rubber or rubberized material and also in other It should be understood that changes may be made in various features of the invention and that certain features may be used without others without departing from the true scope and-spirit of the invention.

Having thus described my invention,.I claim:

1. The method of removing cake from the drum of a rotary nlter which comprises throwing a liquid spray on the peripheral surface of the drum in a direction opposite to the direction of movement of said surface and removing cake in a continuous sheet from said peripheral surface by a rearward and outward brushing action on said peripheral surface in advance of the spraying action.

2. In a rotary nlter, the combination with a rotary nlter drum, of means for stripping nlter cake from the downwardly moving side of the drum including a conveyor belt to receive cake from the drum, transverse ribs on said belt to brush material from the peripheral' surface of the drum, and means beneath the conveyor for throwing a liquid spray upwardly between the conveyor belt and the nlter drum.

3. In a rotary filter, the combination with a rotary filter drum, of means for stripping nlter cake from the downwardly moving portion of. the drum including a conveyor belt to receive cake from the drum, nexible fingers on said belt to brush material .from the peripheral surface of the drum, and means beneath the conveyor belt for throwing a liquid spray upwardly between the conveyor and the nlter drum.

4. In a rotary filter, the combination with a rotary nlter drum, of means for stripping nlter 40 cake from the downwardly moving portion of the drum including a conveyor belt to carry stripped cake away from the drum, means on the conveyor belt to brush cake from the surface of the drum,

and means for throwing a liquid spray upwardly 45 between the conveyor belt and the filter drum. WILLIAM RAISCH. 

